1 /* 2 * Copyright (C) 2017 The Android Open Source Project 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 package com.google.android.exoplayer2.audio; 17 18 import androidx.annotation.Nullable; 19 import com.google.android.exoplayer2.C; 20 import com.google.android.exoplayer2.util.Assertions; 21 import java.nio.ByteBuffer; 22 23 /** 24 * An {@link AudioProcessor} that applies a mapping from input channels onto specified output 25 * channels. This can be used to reorder, duplicate or discard channels. 26 */ 27 /* package */ final class ChannelMappingAudioProcessor extends BaseAudioProcessor { 28 29 @Nullable private int[] pendingOutputChannels; 30 @Nullable private int[] outputChannels; 31 32 /** 33 * Resets the channel mapping. After calling this method, call {@link #configure(AudioFormat)} to 34 * start using the new channel map. 35 * 36 * @param outputChannels The mapping from input to output channel indices, or {@code null} to 37 * leave the input unchanged. 38 * @see AudioSink#configure(int, int, int, int, int[], int, int) 39 */ setChannelMap(@ullable int[] outputChannels)40 public void setChannelMap(@Nullable int[] outputChannels) { 41 pendingOutputChannels = outputChannels; 42 } 43 44 @Override onConfigure(AudioFormat inputAudioFormat)45 public AudioFormat onConfigure(AudioFormat inputAudioFormat) 46 throws UnhandledAudioFormatException { 47 @Nullable int[] outputChannels = pendingOutputChannels; 48 if (outputChannels == null) { 49 return AudioFormat.NOT_SET; 50 } 51 52 if (inputAudioFormat.encoding != C.ENCODING_PCM_16BIT) { 53 throw new UnhandledAudioFormatException(inputAudioFormat); 54 } 55 56 boolean active = inputAudioFormat.channelCount != outputChannels.length; 57 for (int i = 0; i < outputChannels.length; i++) { 58 int channelIndex = outputChannels[i]; 59 if (channelIndex >= inputAudioFormat.channelCount) { 60 throw new UnhandledAudioFormatException(inputAudioFormat); 61 } 62 active |= (channelIndex != i); 63 } 64 return active 65 ? new AudioFormat(inputAudioFormat.sampleRate, outputChannels.length, C.ENCODING_PCM_16BIT) 66 : AudioFormat.NOT_SET; 67 } 68 69 @Override queueInput(ByteBuffer inputBuffer)70 public void queueInput(ByteBuffer inputBuffer) { 71 int[] outputChannels = Assertions.checkNotNull(this.outputChannels); 72 int position = inputBuffer.position(); 73 int limit = inputBuffer.limit(); 74 int frameCount = (limit - position) / inputAudioFormat.bytesPerFrame; 75 int outputSize = frameCount * outputAudioFormat.bytesPerFrame; 76 ByteBuffer buffer = replaceOutputBuffer(outputSize); 77 while (position < limit) { 78 for (int channelIndex : outputChannels) { 79 buffer.putShort(inputBuffer.getShort(position + 2 * channelIndex)); 80 } 81 position += inputAudioFormat.bytesPerFrame; 82 } 83 inputBuffer.position(limit); 84 buffer.flip(); 85 } 86 87 @Override onFlush()88 protected void onFlush() { 89 outputChannels = pendingOutputChannels; 90 } 91 92 @Override onReset()93 protected void onReset() { 94 outputChannels = null; 95 pendingOutputChannels = null; 96 } 97 98 } 99